Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$103.31	3.435%	$106.8587	$106.86	$106.85	$106.90
Purchase #2	$191.74	13.142%	$216.9385	$216.94	$216.95	$216.90
Purchase #3	$38.44	10.314%	$42.4047	$42.40	$42.40	$42.40
Purchase #4	$63.44	10.443%	$70.065	$70.07	$70.05	$70.10
Purchase #5	$5.27	10.607%	$5.829	$5.83	$5.85	$5.80
Purchase #6	$104.83	4.563%	$109.6134	$109.61	$109.60	$109.60
Purchase #7	$116.63	11.624%	$130.1871	$130.19	$130.20	$130.20
7 purchase totals =	$623.66		$681.8964	$681.90	$681.90	$681.90